New Alkylfuranyl-Substituted Benzo[1,2-<i>b</i>:4,5-<i>b</i>′]dithiophene-Based Donor–Acceptor Polymers for Highly Efficient Solar Cells

Abstract

Two new alkylfuranyl-substituted conjugated donor–acceptor polymers—PBDTF-DPP and PBDTF-DPPF—were designed and synthesized. To compare the properties of the new polymers, PBDT-DPP and PBDT-DPPF with alkoxy side chains were also synthesized. The photophysical and electrochemical measurement demonstrated that the alkylfuranyl-substituted polymers had smaller optical band gaps, broader absorption range, and lower HOMO energy levels, thus leading to a larger short current density (Jsc) and higher open circuit voltage (Voc) in photovoltaic devices. Under the same fabricating conditions, the efficiency of the polymer solar cells (PSCs) based on PBDTF-DPP and PBDTF-DPPF reached 3.5% and 5.1%, respectively, whereas PSCs based on PBDT-DPP and PBDT-DPPF only showed an efficiency of 1.0% and 2.9%. After thermal annealing, the efficiency of the PSCs based on PBDTF-DPPF:PC71BM further achieved as high as 6.1%. The results indicate a great potential for largely improving the efficiency of the PSCs by replacing alkoxy with alkyfuranyl group and the building block BDTF in creating exceptional performance materials for PSCs.